Pneumatic calipers used for extruding and clamping hoop, ring washer, pin, cable terminal, cable clip and the like are well known. Pneumatic calipers are particularly familiar in automobile industry, which are used to clamp ring washers onto pipe joint, coupling shaft and similar pieces during the assembling of inner tube and corrugated pipe.
Patent literature records a European patent document of which the application number is 00112559.0 and which then enters China through Patent Cooperation Treaty (PCT) and has a Chinese authorization proclamation No. of CN1264650C, and in which a device for pneumatic operation tool and a pneumatic clamp having the same are provided; this patent provides a pressure medium joint controlled by a valve and a wedge-shaped propulsion piece to control the opening or closing of clip adopting the principle of improving thrust through a plurality of pistons arranged in series to generate moving thrust.
The pneumatic clamp recorded in this patent document, as shown in FIG. 9, includes a clamp base 14, a cylinder 6, a rear base 7, and a clip 1, a wedge-shaped propulsion piece 2, a propulsion piece mounting base 21 for the mounting of the wedge-shaped propulsion piece, a plurality of pistons 3 arranged in series to generate moving thrust and a valve 8 used for controlling the conduction of pressure medium that are arranged along the same axial direction in turn. The clip 1 is fixedly arranged in the clamp base 14; the wedge-shaped propulsion piece 2, the propulsion piece mounting base 21 and the piston assembly all can be moveably arranged in the cylinder along the axial direction; the valve is arranged in the rear base and is in linkage with a valve control 9; the rear base is provided with a pressure medium entrance 71, which can be conducted with the inside of the cylinder 6. The clip 1 includes a first clip 11 and a second clip 12, wherein both the first clip 11 and the second clip 12 have a gripping jaw 111, 121, a strut portion 112, 122, and a mounting portion 114, 124 fixed on the clamp base 14 through a fastening piece 113, 123; one end of the wedge-shaped propulsion piece 2 corresponding to the strut portion 112, 122 is provided with a wedge-shaped side wall 21 to be pushed in between the two strut portions 112, 122 to stretch the two strut portions 112, 122, and one side of the wedge-shaped side wall 21 facing the strut portion 112, 122 forms a small end face, while the other side of the wedge-shaped side wall 21 facing the propulsion piece mounting base forms a big end face.
When this pneumatic clamp works, the pressure medium entrance 71 is in conduction connection with an external pressure medium, and the valve control 9 controls the opening of the valve 8 so that the pressure medium entrance 7 is conducted with the inside of the cylinder 6; then, the pressure medium pushes, as a power source, the piston 3 to move towards the wedge-shaped propulsion piece 2; and then, the wedge-shaped propulsion piece 2 is driven to move towards the clip 1 to be pushed in between the two strut portions 112, 122 to stretch the two strut portions 112, 122, so that the two gripping jaws 111, 121 clamp tightly.
Relevant documents cited in the background of this patent document, for example, DE3742782, DE8900250.4, DE19519543 and DE29509976, also describe this type of pressure medium grip having pressure pistons arranged in series, wherein the clip and the wedge-shaped propulsion piece also adopt the similar structure, that is, the wedge-shaped propulsion piece is pushed in between two strut portions to stretch the two strut portions, so that the two gripping jaws clamp tightly.
For pneumatic gripper, particular for the pressure medium gripper described above, moving thrust is generated in the clip by means of a propulsion tool, for example, the wedge-shaped propulsion piece of the above structure; and the extrusion force of the gripping jaw depends on the thrust of the propulsion tool. However, in existing designs known in conventional art, since the wedge-shaped propulsion piece is pushed in between two strut portions to stretch the two strut portions, and the first clip and the second clip are mounted on the clamp base through two fixed shafts to realize a butting clamping function, two hinging joints are needed, thus manufacturing cost is high, damage is easily caused and the service life is short.